US6373051B1 - Charge inversion mass spectrometry which relies upon the dissociation of a neutral species - Google Patents
Charge inversion mass spectrometry which relies upon the dissociation of a neutral species Download PDFInfo
- Publication number
- US6373051B1 US6373051B1 US09/504,845 US50484500A US6373051B1 US 6373051 B1 US6373051 B1 US 6373051B1 US 50484500 A US50484500 A US 50484500A US 6373051 B1 US6373051 B1 US 6373051B1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/02—Details
- H01J49/10—Ion sources; Ion guns
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/004—Combinations of spectrometers, tandem spectrometers, e.g. MS/MS, MSn
- H01J49/0045—Combinations of spectrometers, tandem spectrometers, e.g. MS/MS, MSn characterised by the fragmentation or other specific reaction
- H01J49/0072—Combinations of spectrometers, tandem spectrometers, e.g. MS/MS, MSn characterised by the fragmentation or other specific reaction by ion/ion reaction, e.g. electron transfer dissociation, proton transfer dissociation
Definitions
- This invention relates to a method of charge inverted mass spectroscopy that is characterized by its ability to differentiate between isomers and other substances that have been impossible to differentiate by the conventional mass spectroscopic techniques.
- the main thrust of mass spectroscopy as compared with other analytical techniques is that it is capable of determining the mass of the molecule of which a certain substance is made while allowing for microanalysis of the substance.
- the conventional techniques of mass spectroscopy have the major drawback of permitting only low resolution in isomer differentiation. Having high resolution in isomer differentiation, the method of the invention allows for differentiation, identification and quantitative determination of many substances in small quantities and finds utility in those areas where analyses have been performed by chromatography and mass spectroscopy.
- Dioxins have different forms of isomers depending upon the substitution position of chlorine atoms and the level of toxicity differs considerably from one isomer to another. With the present technology, it is an extremely painstaking job to separate dioxin isomers and determine their quantities. The efficacy and toxicity of medicines are also variable by great extent from one isomer to another.
- the present invention offers the advantage that individual isomers can be differentiated and quantitatively determined from much smaller quantities of samples than have been required in the prior art technology.
- CID collision-induced dissociation
- CID is a technique relying upon the dissociation of generated ions. Having electrical charge, ions can be analyzed by electromagnetic means such as an electric or magnetic field and, in addition, they are readily detectable. These features make CID suitable for microanalysis. Radical ions, as contrasted with neutral species, have one or more electrons in excess or deficiency, so the activation barrier in the isomerization of radical ions is sufficiently lower than that for neutral species and the former are by far more likely to be isomerized than the latter. “Neutral species” is the generic term for electrically neutral particles and covers not only atoms, molecules, radicals and clusters but also other excited particles that are electrically neutral.
- CID Another feature of CID is that ions are excited to varying internal energy levels and they are dissociated to give a spectrum comprising one dissociated ion superposed on another. This means that although microanalysis is possible by CID, the resolution in isomer differentiation is so low that certain compounds are even impossible to identify.
- the present invention employs a single-electron transfer reaction between an incident positive ion and a target such as an alkali metal that has low ionization energy.
- a target such as an alkali metal that has low ionization energy.
- neutralization with the target takes place as a near resonant reaction whose probability of occurrence is high.
- the generated neutral species in the excited state has a narrow enough energy distribution to increase the likelihood for the occurrence of a specific dissociation.
- the present invention is further characterized in that the neutral species of ion that has been generated by dissociation undergoes a second electron transfer reaction with the target to become a negative ion, which is analyzed and determined quantitatively by mass spectroscopy in an electric or magnetic field.
- This feature contributes to provide a higher resolution in isomer differentiation than the conventional mass spectroscopic technology.
- the method of the invention performs analysis and detection of a particular ion itself and, hence, it allows for analysis and quantitative determination in small quantities, which is one of the salient features of mass spectroscopy.
- a positive ion is generated from an ion source that ionizes a substance such as an isomer, the generated positive ion is mass separated by mass spectroscopy in an electric or magnetic field, the mass separated positive ion is launched into a target chamber filled with a target in the form of alkali metal vapor, charge inversion is allowed to occur in the target chamber to produce a negative ion, the produced negative ion is taken out of the target chamber, and the mass spectrum of the recovered negative ion is analyzed to identify the substance of interest and determine its quantity.
- parent ions ions that result from the intact substance
- fragment ions various ions that result from the broken substance
- the parent ions best reflect the structure of the substance.
- CI chemical ionization
- FAB fast atom bombardment
- a hydrogen ion or an alkali metal ion are attached to the molecule to produce a quasi-molecular ion, which best reflects the structure of the substance (its molecule).
- the quasi-molecular ion can also be introduced into the target chamber.
- FIG. 1 shows electron impact spectra for ortho-, meta- and para-dichlorobenzenes
- FIG. 2 shows CID spectra for ortho-, meta- and para-dichlorobenzenes with Cs used as a target
- FIG. 3 shows charge inverted spectra for ortho-, meta- and para-dichlorobenzenes with Cs used as a target
- FIG. 4 shows CID spectra for ortho-, meta- and para-dichlorobenzenes with K used as a target
- FIG. 5 shows charge inverted spectra for ortho-, meta- and para-dichlorobenzenes with K used as a target
- FIG. 6 shows a CID spectrum and a charge inverted spectrum for CD 3 OH + ;
- FIG. 7 shows a CID spectrum and a charge inverted spectrum for CH 3 OD + ;
- FIG. 8 a shows the internal energy distribution in CID on W(CO) 6 + ;
- the concept of the charge inversion mass spectrometry of the invention may be represented as follows: ion source (generation of a positive ion) ⁇ mass separation of the positive ion (after mass spectroscopy in an electric or magnetic field, the positive ion of interest is mass separated) ⁇ target chamber filled with a target of low ionization energy such as an alkali metal (where the positive ion is converted to a negative ion) ⁇ mass spectroscopy of the negative ion ⁇ detector.
- the charge inversion mass spectrometry of the invention has the advantage of enabling the differentiation of those isomers which have been impossible to differentiate by CID and other conventional mass spectroscopic techniques. This is because the conventional mass spectroscopic techniques involve dissociation from an ion having a broad internal energy distribution whereas the charge inverted mass spectroscopy relies upon dissociation from a neutral species having a very narrow internal energy distribution.
- the method of the invention also differs from the conventional techniques in that a target of low ionization energy such as an alkali metal is introduced in vapor form into the target chamber and that the incident ion is a positive ion whereas an oppositely charged negative ion is detected.
- the positive ion is generated in the ion source.
- any of the ionization methods used in mass spectroscopy may be employed, as exemplified by electron impact ionization, chemical ionization and fast atom bombardment.
- the generated positive ion is subjected to mass spectroscopy in an electric or magnetic field.
- the mass separated positive ion is launched into the target chamber filled with the vapor of a target of low ionization energy such as an alkali metal.
- a negative ion is produced by one of two processes.
- a single-collision, double electron transfer process which is linearly proportional to the density of the vapor of a target of low ionization energy such as an alkali metal, dissociation does not usually accompany and the cross-sectional area for the generation of negative ions is small.
- the other process is a double collision, successive single-electron transfer process which is proportional to quadratic dependence the density of the target vapor.
- an excited neutral species is generated by a near resonant electron and dissociated into neutral fragments, which in turn collide with another target such as an alkali metal to produce a negative ion by a second occurrence of the single-electron transfer.
- dissociation occurs after neutralization and its pattern varies not only with the positive ion of an isomer but also with the type of the target vapor (whether it is an alkali metal or something else).
- the resulting negative ion leaves the target chamber.
- the emerging negative ion is subjected to mass spectroscopy before it is detected. In this manner, the generated negative ion undergoes mass spectroscopy to yield a charge inverted spectrum for the isomer of interest.
- Electron transfer between an ion (or neutral species) in flight and the target is initiated by collision. If a single collision causes transfer of two electrons at a time, the process is called “single-collision, double electron transfer”. Since a negative ion results from a single collision, the process is in linear proportion to the density of the vapor of the target such as an alkali metal.
- double-collision, continuous single-electron transfer a positive ion undergoes one collision with the target to become a neutral species, with single-electron transferred, and the resulting neutral species (to be exact, a neutral species dissociated from that neutral species) collides with another target to become a negative ion, with another electron being transferred. Since two target collisions occur, the process is proportional to quadratic dependence the density of the vapor of the target such as an alkali metal and the dissociation of the second neutral species from the first neutral species enables the method of the invention to distinguish between isomers.
- one target chamber is used.
- charge inverted mass spectroscopy can also be performed using two target chambers. In this case, different targets may be employed in the two target chambers.
- both an incident positive ion and a negative ion to be detected are analyzed.
- the apparatus has the second mass spectrometer that allows for analysis of positive ions.
- Negative ions can be analyzed by the same method except for the polarities of electric and magnetic fields to be applied.
- positive and negative ions are analyzed by a sector arrangement using an electric field and a magnetic field. Instead, the quadruple, ion trap and all other conventional methods of mass spectroscopy may be substituted.
- Controlling the density of the vapor of the target such as an alkali metal is critical to the invention. If the density is unduly low, the intensity of a negative ion relative to a positive ion is insufficient to produce a spectrum with adequate intensity of negative ions. If the density is excessive, the incident ion and the generated negative ion are scattered by multiple collisions and too much attenuated to produce high spectral resolution.
- the results shown in the examples that follow are those obtained by using alkali metals Cs and K as the target. Similar results are obtained with other alkali metals such as Li, Na and Rb that have low ionization energy.
- ortho-, meta- and para-dichlorobenzenes give identical spectra and cannot be differentiated from one another. This is not the case with the charged inverted mass spectroscopic method of the invention and those isomers can be clearly differentiated.
- FIG. 1 shows electron impact spectra for ortho-, meta- and para-dichlorobenzenes
- FIGS. 2 and 3 show CID and charge inverted spectra, respectively, for the same isomers with Cs used as a target
- FIGS. 4 and 5 show CID and charge inverted spectra, respectively, for the same isomers with K used as a target.
- the isomerism of ortho-, meta- and para-dichlorobenzenes depends on the substitution position of chlorine atoms on the benzene ring.
- the clear distinction that is observed between the charge inverted spectra for these isomers suggests the possibility for analysis and determination in small quantities of dioxins and other isomeric substances by mass spectroscopy.
- FIG. 6 shows a CID spectrum and a charge inverted spectrum for CD 3 OH +
- FIG. 7 shows a CID spectrum and a charge inverted spectrum for CH 3 OD + .
- the CH 3 OH + ion whether it is in a CID spectrum or a charge inverted spectrum, has a predominant peak at a mass number of 31 with one hydrogen atom eliminated and the other peaks are very weak.
- the CID spectrum of the CD 3 OH + ion substituting deuterium for each of the hydrogen atoms in the methyl group shows only the CD 2 OH + ion (mass number decreased by 2) and the presence of the CD 3 O + ion (mass number decreased by 1) is negligible.
- the charge inverted spectrum of the CD 3 OH + ion shows only the CD 3 O ⁇ ion (mass number decreased by 1) and the presence of the CD 2 OH ⁇ ion (mass number decreased by 2) is negligible.
- the CID spectrum of the CH 3 OD + ion substituting deuterium for the hydrogen atom in the hydroxyl group shows only the CH 2 OD + ion (mass number decreased by 1) and the presence of the CH 3 O + ion (mass number decreased by 2) is negligible.
- the charge inverted spectrum of the CH 3 OD + ion shows only the CH 3 O ⁇ ion (mass number decreased by 2) and the presence of the CH 2 OD ⁇ ion (mass number decreased by 1) is negligible.
- Neutral molecules usually have closed electron shells and, hence, their isomerization energy is higher than that of radical cations with open shells.
- Charge inverted mass spectroscopy depends on the dissociation of a neutral molecule which is less likely to be isomerized than ions and this is why isomers can be differentiated at high resolution by charge inverted mass spectroscopy as demonstrated in Example 1.
- a compound like W(CO) 6 which is commonly called a “thermometer molecule” has been used to measure the internal energy distributions of ions generated in electron impact spectra, CID spectra and surface-induced dissociation (SID) spectra.
- FIG. 8 a shows the internal energy distribution in CID on W(CO) 6 + (Cs used as target) together with documented data for CID spectra that were obtained with Ar used as the target.
- CID internal energy distribution in CID agrees with the documented data for the use of Ar as target and it is broad enough to show a progressive decrease in intensity as the incident energy increases. This means that CID spectra consist of superposed contributions from various mechanisms of dissociation involving different internal energies.
- the internal energy distribution in charge inverted mass spectroscopy is concentrated in a position that is lower than the energy level of the incident ion by 3.89 eV which is the ionization energy of Cs and the half-peak width of energy is as small as about 2 eV.
- Isomers can be differentiated and quantitatively determined with far smaller quantities of samples than have been required in the conventional methods
- Isomers can be differentiated at high resolution by mass spectroscopy while retaining its capability for microanalysis.
- Dioxins and other isomeric substances can be analyzed and quantitatively determined in small quantities by mass spectroscopy.
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Abstract
Description
Claims (6)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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JP11-038397 | 1999-02-17 | ||
JP11038397A JP2000241390A (en) | 1999-02-17 | 1999-02-17 | Charge exchange mass spectrometry using dissociation of neutral species |
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US6373051B1 true US6373051B1 (en) | 2002-04-16 |
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US09/504,845 Expired - Fee Related US6373051B1 (en) | 1999-02-17 | 2000-02-16 | Charge inversion mass spectrometry which relies upon the dissociation of a neutral species |
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JP (1) | JP2000241390A (en) |
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Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060009915A1 (en) * | 2000-12-26 | 2006-01-12 | Institute Of Systems Biology | Rapid and quantitative proteome analysis and related methods |
US20070015158A1 (en) * | 2003-05-30 | 2007-01-18 | Mcluckey Scott A | Process for increasing ionic charge in mass spectrometry |
US20080048109A1 (en) * | 2006-08-25 | 2008-02-28 | Schwartz Jae C | Data-dependent selection of dissociation type in a mass spectrometer |
US20110062324A1 (en) * | 2002-07-24 | 2011-03-17 | Micromass Uk Ltd | Mass spectrometer with bypass of a fragmentation device |
US9117643B2 (en) | 2010-02-22 | 2015-08-25 | Osaka University | Alkali metal introduction apparatus and alkali metal introduction method |
CN104965020A (en) * | 2015-05-29 | 2015-10-07 | 中国科学院计算技术研究所 | Multistage mass spectrum biomacromolecule structure identification method |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB0523811D0 (en) * | 2005-11-23 | 2006-01-04 | Micromass Ltd | Mass stectrometer |
GB0523806D0 (en) * | 2005-11-23 | 2006-01-04 | Micromass Ltd | Mass spectrometer |
WO2017179147A1 (en) * | 2016-04-13 | 2017-10-19 | 株式会社島津製作所 | Isomer analysis method using mass spectrometry, and tandem mass spectrometer |
Citations (3)
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US4731533A (en) * | 1986-10-15 | 1988-03-15 | Vestec Corporation | Method and apparatus for dissociating ions by electron impact |
SU1067972A1 (en) | 1981-06-18 | 1992-05-07 | Предприятие П/Я А-7797 | Method of producing negative ions |
US5545894A (en) | 1995-05-04 | 1996-08-13 | The Regents Of The University Of California | Compact hydrogen/helium isotope mass spectrometer |
-
1999
- 1999-02-17 JP JP11038397A patent/JP2000241390A/en active Pending
-
2000
- 2000-02-16 US US09/504,845 patent/US6373051B1/en not_active Expired - Fee Related
- 2000-02-17 GB GB0003774A patent/GB2347012A/en not_active Withdrawn
Patent Citations (3)
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SU1067972A1 (en) | 1981-06-18 | 1992-05-07 | Предприятие П/Я А-7797 | Method of producing negative ions |
US4731533A (en) * | 1986-10-15 | 1988-03-15 | Vestec Corporation | Method and apparatus for dissociating ions by electron impact |
US5545894A (en) | 1995-05-04 | 1996-08-13 | The Regents Of The University Of California | Compact hydrogen/helium isotope mass spectrometer |
Non-Patent Citations (13)
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S. Hayakawa et al., "A New Technique to Study the Dissociation of Energy-Selected Neutral Intermediates" International Journal of Mass Spectrometry, vol. 202, pp. A1-A7 (2000). |
S. Hayakawa et al., "Definitive Evidence for the Existence of a Long-Lived Vinylidene Radical Cation, H2C=C+" The Journal of Chemical Physics, vol. 110, pp. 2745-2748 (1999). |
S. Hayakawa et al., "Discrimination of Isomers of Dichlorobenzene Using Charge Inversion Mass Spectrometry", J. Mass Spectrom. Soc. Japan, in press (2000). |
S. Hayakawa et al., "Dissociation Mechanism of Electronically Excited C3H4 Isomers by Charge Inversion Mass Spectrometry", International Journal of Mass Spectrometry and Ion Processes, 171 (1997) 209-214. |
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Cited By (15)
Publication number | Priority date | Publication date | Assignee | Title |
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US20060009915A1 (en) * | 2000-12-26 | 2006-01-12 | Institute Of Systems Biology | Rapid and quantitative proteome analysis and related methods |
US8909481B2 (en) | 2000-12-26 | 2014-12-09 | The Institute Of Systems Biology | Method of mass spectrometry for identifying polypeptides |
US9196466B2 (en) | 2002-07-24 | 2015-11-24 | Micromass Uk Limited | Mass spectrometer with bypass of a fragmentation device |
US10083825B2 (en) | 2002-07-24 | 2018-09-25 | Micromass Uk Limited | Mass spectrometer with bypass of a fragmentation device |
US9697995B2 (en) | 2002-07-24 | 2017-07-04 | Micromass Uk Limited | Mass spectrometer with bypass of a fragmentation device |
US20110062324A1 (en) * | 2002-07-24 | 2011-03-17 | Micromass Uk Ltd | Mass spectrometer with bypass of a fragmentation device |
US9384951B2 (en) | 2002-07-24 | 2016-07-05 | Micromass Uk Limited | Mass analysis using alternating fragmentation modes |
US8809768B2 (en) | 2002-07-24 | 2014-08-19 | Micromass Uk Limited | Mass spectrometer with bypass of a fragmentation device |
US7550718B2 (en) * | 2003-05-30 | 2009-06-23 | Purdue Research Foundation | Process for increasing ionic charge in mass spectrometry |
US20070015158A1 (en) * | 2003-05-30 | 2007-01-18 | Mcluckey Scott A | Process for increasing ionic charge in mass spectrometry |
US8168943B2 (en) * | 2006-08-25 | 2012-05-01 | Thermo Finnigan Llc | Data-dependent selection of dissociation type in a mass spectrometer |
US20080048109A1 (en) * | 2006-08-25 | 2008-02-28 | Schwartz Jae C | Data-dependent selection of dissociation type in a mass spectrometer |
US9117643B2 (en) | 2010-02-22 | 2015-08-25 | Osaka University | Alkali metal introduction apparatus and alkali metal introduction method |
CN104965020A (en) * | 2015-05-29 | 2015-10-07 | 中国科学院计算技术研究所 | Multistage mass spectrum biomacromolecule structure identification method |
CN104965020B (en) * | 2015-05-29 | 2017-07-21 | 中国科学院计算技术研究所 | Multi-stage mses structure of biological macromolecule authentication method |
Also Published As
Publication number | Publication date |
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GB2347012A (en) | 2000-08-23 |
GB0003774D0 (en) | 2000-04-05 |
JP2000241390A (en) | 2000-09-08 |
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